BOOK I PART III
we may easily conceive, that there is no abso-
lute nor metaphysical necessity, that every be-
ginning of existence should be attended with
such an object. If we define a cause to be, _an
object precedent and contiguous to anothe, and
so united with it in the imagination, that the
idea of the one determines the mind to form
the idea of the other, and the impression of the
one to form a more lively idea of the other; we
shall make still less difficulty of assenting to
this opinion. Such an influence on the mind is
in itself perfectly extraordinary and incompre-
hensible; nor can we be certain of its reality, but
from experience and observation.
I shall add as a fourth corrollary that we can
never have reason to believe that any object
exists, of which we cannot form an idea. For
as all our reasonings concerning existence are